A sphere of mass 𝑚 is tied to end of a string of length 𝑙 and rotated through the other end along ahorizontal circular path with speed 𝑣. The work done in full horizontal circle is

Question : A sphere of mass 𝑚 is tied to end of a string of length 𝑙 and rotated through the other end along a horizontal circular path with speed 𝑣. The work done in full horizontal circle is

(A) 0

(B) $\dfrac{mv^{2}}{l}.2\pi l$

(C) $mg\cdot 2\pi$

(D) $\left( \dfrac{3v^{2}}{l}\right) \cdot \left( l\right)$